Knife holder for lathes



Oct. 31, 1961 H. F. ELFORD 3,006,392

KNIFE HOLDER FOR LATI-IES Filed March 15. 1959 Harold Fflf'ord IN V ENTOR.

United States Patent Ofifice 3,006,392 Patented Oct. 31, 1961 3,606,392KNIFE HOLDER FDR LATI-IES Harold F. Elford, Portland, Oreg., assignor toElford Plywood Machinery, Inc., Portland, Oreg., a corporation of OregonFiled Mar. 13, 1959, Ser. No. 799,141 7 Claims. (Cl. 144212) Thisinvention relates to veneer lathes, and more particularly to an improvedconstruction for mounting the cutting knife (or knives) of a veneerlathe, wherein the knife may be readily removed for sharpening andsubsequently set back on the lathe and secured in fixed position, with aminimum amount of adjustment and down time.

Veneer lathes used in cutting a thin sheet of veneer from a peeler logconventionally have an elongated knife (or, in some instances, a seriesof aligned knife sections) which is held fast while the log periphery isrotated against the knife for the production of a veneer sheet. It isimportant that the knife be securely held, so that the veneer sheetproduced will be of uniform thickness. In addition, it is necessary thatthe knife be sharp, in order for a clean cut to'be made. The necessityfor maintaining the edge of the knife sharp has dictated the use of adetachable knife, which may be removed at intervals and then sharpenedwhile separated from the lathe. The mounting for the knife should bereadily detachable and also be capable of firmly holding the knife inplace.

. Conventional knife mountings have had the disadvan- -tage of requiringextensive adjustment every time the knife .is removed and thenremounted. Adequate supportfor a knife has also sometimes been lacking.In-

adequate provision for the support of a knife has made 1 necessary theuse of relatively thick, heavy knives, which are more costly and requirea longer time to sharpen.

Generally, it is an object of this inventionr to provide an improvedknife holder construction which firmly holds a relatively thin kniferigidly throughout its length, and

which enables speedy dismounting and remounting of the knife.

A more specific object of the invention is to provide a knife-holderconstruction wherein the knife throughout its length is held in place bymeans of a plurality of novel clamping members or levers, each of whichis camactuated by a novel cam mechanism into clamping engagement withthe knife to hold the knife in place.

Another object of the invention is to provide a construction whereineach of the clamping members is provided with a pivotable clamping shoeportion at that end which bears against the knife, this clamping shoeportion being operable to distribute clamping pressure from the clampinglever to the knife over an enlarged area, without producing high and lowpressure spots. The pivot connection enables the shoe to yield as ittransmits a clamping force from the clamping member to the knife.

In an embodiment of the invention, it is contemplated that each clampingmember have a separate cam mechanism, each of which may be actuatedindependently of the others. Thus the amount of clamping pressuregenerated by a given clamping member is determined by the extent the cammechanism for the member is turned. The cam mechanism also. features aslidable mounting for the rotatable cam of the mechanism, whichaccommodates shifting movement of the cam rotation axis to ward and awayfrom the pivot axis for its associated clamping member. This enables therotatable cam to slide and to center itself with respect to a cuppedwear surface which is provided the clamping member and which engages thecam surface of the cam. The cupped wear surface provides a bigger areaof'contact with the cam and makes possible a firmer grip between theclamping member and cam. The shifting action allowed the cam takes careof the tendency of the cupped Wear surface to shift out of alignmentwith the cam rotation axis due to the pivotal movement which is allowedthe clamping member. The loose mounting for the cam rotation axis alsosimplifies problems of installation.

Another feature of the invention is the Provision of a pivot mountingfor each of the pivoted clamping levers or members which accommodatesadjustment of the pivot axis for the member in a direction toward andaway from a plane passing through the cutting knife. This adjustmentprovides a means for setting the clamping pressure produced by theclamping member when the cam is turned to approximately an overcenterposition, which is the optimum position for the parts with the knifeclamped in place, as this overcenter position is the most stable. Thepivot mounting for the clamping shoe portion for each clamping member isimportant in conjunction with this adjustment feature, due to the factthat adjustment of the pivot axis for a clamping lever would have theelfect of repositioning the face of the clamping shoe with respect tothe knife if this clamping shoe were fixed in position on the end of theclamping member. The adjustability of the pivot axis for the clampinglever is also important in conjunction with the sliding mounting for thecam for actuating the lever, since it enables the cam to truly centeritself in the cupped wear surface irrespective of the position of theclamping lever pivot axis.

This application is a continuation-in-part of an application filedNovember 8, 1957 having Serial No. 695,263, and now abandoned andentitled, Knife Holders for Wood Veneer Lathes.

Other objects, advantages, and features of the invention will becomeapparent as the following description is read in conjunction with theaccompanying drawings wherein:

FIG. 1 is an end elevation of a Veneer lathe and knife holderconstructed according to an embodiment of this invention, with portionsbroken away to illustrate details of construction;

FIG. 2 is a front view of portions of the knife-holding mechanismillustrated in FIG. 1;

FIG. 3 is a view corresponding to the view of FIG. 2 but illustratinganother embodiment of the invention;

FIG. 4 is a side view of the knife-holding mechanism illustrated in FIG.3;

FIG. 5 is a perspective view of portions of the camactuating mechanismused in the construction of FIGS. 3 and 4; and

FIG. 6 is a perspective view of another portion of the samecam-actuating mechanism. Referring now to the drawings for a descriptionof the mvention, and in particular to FIGS. 1 and 2, 10 indicatesgenerally a veneer lathe of the type used in peeling thin sheets ofveneer from a peeler log, the log being indicated in dotted outline at11. The log is supported on the lathe on suitable spindles, exemplifiedby the spindle shown in outline at 12.

The lathe includes a frame or mounting base 16 of an inverted, V-shapedcross section, as can best be seen by the outline shown in FIG. 1. Theframe supports a knife 17 and holder mechanism, generally indicated at18. Frame 16 has a front wall 20 mounting the knife holder mechanism,and a sloping rear wall 21, which provide support for a veneer sheet cutby the lathe as it travels away from log 11.

The lathe also includes a nose bar 26 which rides against the peripheryof a log during cutting, and functions to steady the log so as toprevent thick and thin cutting. Normally the lathe is provided withsuitable mechanism for moving frame 16 toward and away from theperiphery of the log held by spindles 12, to compensate for thereduction in diameter of the log which occurs during cutting. Thismechanism is not illustrated, as it forms no part of the invention.

Concerning the knife and holder mechanism, knife 17 is supported onframe 16 with one of its faces abutting a backing plate 31. The backingplate extends along the rear of the knife substantially the length ofthe knife, and when assembled on the lathe, constitutes part of themounting base for the knife.

Arranged along the forward or other face of the knife is a clampingplate 32. The clamping plate in the embodiment-illustrated has a lengthwhich is substantially equal to the length of the knife and backingplate 31. The backing and clamping plates (which constitutes braceplates in the device) provide two rigid surfaces on either side of theknife, which act to make the knife rigid when the two surfaces arebrought together. Thus, using the construction contemplated, arelatively thin knife may be employed, which is easy to sharpen; andthis type of knife may be used without the disadvantages normallyattending such use, i.e., appreciable flexing of the knife during thecutting operation.

An elongated support bar 37 supports the lower edge of knife 17. The baris movable up and down on the frame by means of jack screws 38 mountedat intervals on'frame 16 beneath the support bar with their upper endsabutting the bar. Thus, when the knife is sharpouter ends of the bolts46 and washers 48 seat in dishedout recesses 47 formed in the clampingmembers. The bolt connection described for each clamping memberaccommodates pivotal movement of the member about an axis extendingtransversely of the bolt and substantially parallel to the length ofknife 17.

Bolts 46 may be backed out of front wall 20, with the effect of movingthe pivot axis for the clamping levers away from the front wall, or tothe right in FIG. 1. Thus the bolts constitute means having adjustmentmechanism accommodating adjustment of the pivot axes for said memberstoward and away from a plane passing through the knife. This adjustmentis important in connection with the cam-actuating mechanism for eachlever, to be described below. The adjustment also is important inconjunction with the pivotal mounting of the brace plate 32 on the upperends of the levers, since movement of the pivot axis for the leverstoward or away from the plane ened and returned to the lathe, the jackscrews may be turned so as to raise with the bar and the sharpened edgeof the knife supported thereon until the knife edge is properlypositioned for cutting.

Holder mechanism 18 further comprises a plurality of elongated clampingmembers or levers. 36, arranged side by side and extending in a row.These levers extend substantially transversely of the knife. Only aportion of the clamping levers are illustrated in FIG. 2 for reasons ofsimplicity. It should be realized that, in practice, knife 17 isrelatively long, and as many as 8 to 12 clamping members may be presentin a conventional lathe. These clamping levers are loosely carried onthe front Wall 20 of the lathe, by means to be described.

The clamping levers have upper ends which engage clamping plate 32.These upper ends are also pivotable relative to this clamping plate. Theplate constitutes a pressure shoe operable to transmit to the knifepressures produced by the clamping levers. The pivot allowed between theupper end of each clamping lever and the plate orvshoe 32 is important,as it enables angular shifting of the clamping plate to a positionwherein its entire inner surface abuts the plane of the outer face ofknife 17. Were a rigid connection employed, either the top or bottomedge of the pressure plate might hear heavily against the knife with theother edge riding almost free of the knife, the exact conditionresulting depending upon the thickness of the knife and upon theposition of the pivot axis for the clamping levers relative to the planeof the knife. Thus each clamping member or lever is provided at itsupper end with a rounded shoulder 41 which extends transversely acrossthis upper end. The shoulders 41 of the various clamping levers fit intoan elongated groove 42 prepared in the outer face of clamping shoe orplate 32 and rotate within this groove. Clamping members 36 may besecured directly to the plate, as by screws 43 in serted throughaccommodating, loosely fitting bores provided in the upper ends of themembers. A pair of compression springs 44 are also shown, which keepeach clamping member 36 snugly against plate 32, while permittingball-and-socket type of movement between the CWO.

.As already stated, the clamping members are pivotly connected immediatetheir ends to mounting base 16. The connection is made through bolts 46which are secured to wall 20. A pair of these bolts are shown for eachclamping lever, and these are inserted through loosely fitting bores 46aprovided in the clamping levers. The

of knife 17 has the effect of changing the angular relationship of theselevers and the plane of knife 17.

In the embodiment of FIGS. 1 and 2, each clamping member is biased toswing in a clockwise direction in FIG. 1 and away from a clampingposition by a nut and bolt assembly 51 and spring 52. Each assembly 51is threaded through an enlarged bore formed in wall 20 of the frame.Spring 52 encircles the bolt portion of assembly 51 and is seatedbetween a set of washers 53.

In the embodiment of FIGS. 1 and 2, the clamping members are swungsimultaneously about their pivot connections and into the clampingposition of FIG. 1 by a cam-actuated mechanism, indicated generally at61. Mechanism 61 comprises an elongated shaft 62 extending along thelength of the knife beneath the knife and having a handle 63 atfixed toone end thereof. The shaft is rotatably mounted on the front face ofwall 20 in plural brackets 64, which are slidable up and down on thefront face of wall 20.

Joined to shaft 62 and spaced along the length of the shaft are aplurality of cam elements 71. These are cylindrical in shape, and aremounted on shaft 62 with their axial centers off-set from the axialcenter of shaft 62. Rotation of the shaft operates to rotate the camelements in unison. Each of the cam elements has a cylindrical camsurface which is rotatable within a cupped wear surface portion 72provided at the base or the lower end portion of each member. The cuppedwear surface provides an enlarged area of contact between the lower armof each clamping lever and its associated cam, and this extended area ofcontact means that the cam memher, when moved to a position causingclamping pressure in a clamping member, tends firmly to be held inplace, and is prevented from gradually loosening. The cam constructionand wear surface described is to be distinguished from a cam mechanismwherein only line contact between a cam and the surface it engages isprovided.

It will be noted that. as the lever members are pivoted about the pivotconnections provided by bolts 46, the lower ends of the levers move tothe right in FIG. 1, and also slightly upwardly, due to the arcuatemovement which results from their pivot mounting. As a result, somevertical shifting of the cupped wear surfaces occurs relative to frontwall 20. It is for this reason that the cam members and cam shaft aresupported on the front of wall 20 by means which accommodates shiftingof these parts toward and away from the pivot axes for the clampingmembers 36. By providing for this shifting or sliding movement, the camstend to center themselves in the respective wear surfaces and maximumoutward pressure on the lower end of the clamping levers occurs when thecams are moved approximately to a true overcenter position. This isdesirable, as it is in this position that the cams are most firmly heldand prevented from joggling to a position wherein loosening takes place,

With the mounting just described, for any given knife thickness, bolts46 are adjusted so that, in approximately a truly overcentered positionfor the cams, the requisite clamping pressure exists in the upper endsof the levers. After adjustment, the knife used is easily removed afterfirst swinging the cams away from their overcenter position. The knifeis readily remounted and held fixedly in place with the same clampingpressure as previously, by swinging the cams back to their overcenterposition.

Referring now to FIGS. 3, 4, 5 and 6, these figures illustrate anotherembodiment of the invention. In this embodiment, the clamping members orlevers are pivoted into clamping engagement independently of each other,by means of a separate cam-actuating mechanism provided each member.Further, a segmented clamping plate, i.e., plural clamping shoes areemployed.

Considering now this embodiment, the knife 17 is held in place by aplurality of clamping members 81. These clamping members are pivotedintermediate their ends on the front face of the wall 20 by nut and boltassemblies 82. The pivot connections for members 81 is similar to thepivot connections already described for clamping members 36, and eachaccommodates shifting of the pivot axis for a clamping member in adirection away from the plane of knife 17.

At the upper or clamping end of each clamping member is an individualclamping shoe 86. Each has an elongated groove 87 which fits over atransverse shoulder 88 at the upper end of the clamping member. Theshoes are held in place by side clips 89 having turned over, outer ends,and inner ends welded to the shoe. The shoulder and groove accommodatepivotal movement between each clamping shoe and the upper end of itsassociated clamping member, similar to the movement described inconjunction with the first embodiment.

The lower end of each clamping member 81 is bifurcated, and terminatesin two leg portions 91, 92. Each leg portion has, on the inner sidethereof, a cupped wear surface 96. These cupped wear surfaces performthe function of wear surfaces 72 of clamping members 36.

Held in the space between the front face of wall 20 and the inner sideof each clamping member is a cam shaft treating element 101, a stub camshaft 102, and a T-shaped double cam element 103. These parts constitutethe camactuating mechanism for each clamping member. The parts are heldloosely adjacent the face of front wall 20, with the seating elementfree to slide up and down on the wall, to accommodate vertical shiftingof the rotation axis for the cams.

Shaft seating element 101 (shown disassembled from the mechanism in FIG.5) abuts the outer face of wall 20. The shaft seating element hasmounting portions 111, 112 at its ends, which are provided with suitablebores 113 for the reception of the ends of shaft 102.

Shaft seating element 101 mounts shaft 102 and double cam element 103(the two latter parts are shown separate from the rest of the mechanismin FIG. 6) with shaft 102 inserted through bores provided in eleme 103as shown in FIG. 6. When the entire cam mechanism is assembled as inFIGS. 3 and 4, the central portion of shaft 102 engages and rotatesagainst a semicylindrical built-up surface 116 of element 101, and theends of the shaft 102 extend outwardly through the bores 113. Portions117, 118 to either side of surface 116 and inwardly of mounting portions111, 112 are concavely configured, and receive cylindrically surfaced,cam ends 119 of element 103 without contacting the same. The cylindricalsurfaces of the cam ends of element 103 are aligned on a common axis,which is offset from the center axis of shaft 102.

In operation, rotation of cam element 103 functions to move the surfacesof ends 119 against wear surfaces 96, and this is accompanied by pivotalmovement of a clamping member in a clamping direction. The reactionforce created by movement of the cam ends against wear surfaces 96 istransmitted through stub shaft 102 to seating element 101, and fromthence to wall 20.

Double cam element 103 has a center leg 12-1 which takes the shape of asocket for a handle (indicated in outline in FIG. 4). .Handle 122 isremovable from the socket, and thus may be used for rotating all thecam-actuating mechanisms for the various clamping levers.

In some veneer lathes, instead of one elongated knife, several knifesections laid end to end are employed. The use of separate andindependently operable cam-actuating mechanisms for each clamping leverenables the removal of one knife section independently of the remainder,which is an important advantage.

While there has been described several embodiments of the invention, itis recognized that changes in the parts and their arrangement arepossible, without departing from the spirit of the invention. It isdesired to cover all modifications and variations which would beapparent to one skilled in the art, and that come within the scope ofthe appended claims.

It is claimed and desired to secure by Letters Patent:

1. In a veneer lat-he, the combination of a mounting base; an elongated,relatively thin knife supported thereon; a plurality of elongatedclamping members arranged transversely of said knife with one set ofends overlapping one side of said knife; means pivotally connecting theclamping members intermediate their ends to said mounting base forpivotal movement of the members about pivot axes extending substantiallyparallel to the length of said knife; the latter means having adjustmentmechanism accommodating adjustment of the pivot axes for said memberstoward and away from a plane passing through said knife; pivotablepressure shoe means pivotable relative to said overlapped set of ends ofsaid clamping members interposed between said knife and said overlappedset of ends and operable to transmit pressure from said set of ends tosaid knife; and a rotatable cam for each clamping member mounted betweeni the other end of the member and said mounting base operable onrotation of the cam to generate clamping pressure in the clampingmember; each cam having a shiftable mounting accommodating shifting ofits rotation axis toward and away from the pivot axis for the clampingmember simultaneously with rotation of the cam.

2. In a veneer lathe, a mounting base; an elongated knife supportedthereon; a plurality of elongated clamping members arranged transverselyof said knife with one set of ends overlapping one side of said knifeand their other set of ends disposed downwardly therefrom; adjustablescrew means extending through an intermediate portion of each clampingmember securing the same to said mounting base; said adjustable screwmeans pivotally supporting the clamping member for pivotal movementabout an axis extending parallel to the length of said knife andaccommodating adjustment in the position of the pivot axis toward andaway from a plane passing through said knife; pivotable pressure shoemeans pivota-ble relative to said overlapped set of ends of saidclamping members interposed between said knife and said overlapped setof ends and operable to transmit pressure from said set of ends to saidknife; a cam for each clamping member and a mounting for the camrotatably supporting the cam between said mounting base and the otherend of the member; the mounting for the cam including shiftable meansenabling shifting movement of the cam on said mounting base toward andaway from the pivot axis for the clamping member; and means foractuating the cam for each clamping member independently of the cams forthe other clamping members.

3. In a veneer la-the having a frame portion, a knife supported on theframe portion, and plural clamping lever portions pivoted on the frameportion for clamping the knife to the frame portion, the improvementcomprising cam mechanism for each clamping lever portion for generatingclamping pressure in the lever portion by pivoting of the clamping leverportion, said cam mechanism comprising a rotatable cam having a curvedcam surface and a mounting for the cam rotatably supporting the cam,said mounting for the cam being supported on one of said portions andincluding shiftable means accommodating shifting of the cam rotationaxis toward and away from the pivot axis for the clamping lever portionsimultaneously with rotation of the cam, and a curved wear surfaceprovided the other of said portions contacting the cam surface of thecam and constructed to be pressed on by said cam surface on rotation ofsaid cam.

4. In a veneer lathe having a frame, a knife supported on the frame, andplural clamping levers pivoted on the frame for clamping the knife tothe frame, the improvement comprising cam mechanism for each clampinglever for generating clamping pressure therein, said cam mechanismcomprising a cam having a curved cam surface anda mounting for the camrotatably supporting the cam, said mounting being supported on saidframe and including shiftable means accommodating shifting movement ofthe cam rotation axis toward and away from the pivot axis for theclamping lever simultaneously with the rotation of the cam, and a curvedwear surface provided the clamping lever contacting the cam surface ofits cam.

5. In a veneer lathe having a frame portion and a knife supported on theframe portion, plural clamping lever portions for clamping the knife tosaid frame portion, a pivot connection connecting each clamping leverportion to the frame portion, said pivot connection having adjustmentmechanism accommodating shifting of the pivot axis for the lever portiontoward and away from a plane passing through said knife, and cammechanism for each clamping lever portion for generating clampingpressure therein by pivoting of the clamping lever portion, said cammechanism comprising a cam having a curved cam surface and a mountingfor the cam rotatably supporting the cam, said mounting being supportedon one of said portions and including shiftable means accommodatingshifting movement of the cam rotation axis toward and away from thepivot axis for the clamping lever portion simultaneously with rotationof the cam, and a curved wear surface provided said other portioncontacting said Cent surface and constructed to be pressed on by saidcam surface on rotation of said carn.

6. In a veneer lathe having a frame, a knife supported on the'frame, andplural clamping levers pivoted on the frame for clamping the knife tothe frame, the improvement comprising cam mechanism for each clampinglever for generating clamping pressure in the lever, said cam mechanismcomprising a camhaving a cam surface and a cam shaft joined to said cam,a seating member slidable on the frame rotatably mounting the cam shaft,a cupped wear surface provided on the clamping lever, said cupped wearsurface contacting the cam surface of the cam, and means operativelyconnected to the cam shaft and cam for rotating the same.

'7. In a veneer lathe, the combination of a mounting base; an elongated,relatively thin knife supported on said -mounting base; and clampingmeans for clamping rigidly the knife to said mounting base; saidclamping means comprising an elongated brace plate substantiallycoextensive in length with said knife mounted over one side of saidknife and making the same rigid; and a plurality of clamping membersarranged transversely of the knife and pivotaliy connected intermediatetheir ends to said mounting base; the pivot connections for saidclamping members accommodating pivotal movement of the members aboutaxes extending substantially parallel to the length of the knife andhaving means enabling adjustment of these pivot axes toward and awayfrom a plane passing through the knife; said clamping members beingspaced at regular intervals along the length of the knife; each of theclamping members having an end portion overlapping the brace plate andconnected to the brace plate by means accommodating pivotal movementbetween the two; and cam means operatively interposed between eachclamping member and the mounting base for generating clamping pressurein the clamping member.

References Cited in the file of this patent UNITED STATES PATENTSGermany Sept. 10, 1930

